Showing papers on "Coordination polymer published in 2022"

Hierarchical Hollow Zinc Oxide Nanocomposites derived from Morphology-tunable Coordination Polymers for Enhanced Solar Hydrogen Production.

Abstract: As the flexible producer of substrates, it is of increasing importance to create the infinite coordination-polymer particles (CPPs) for high-efficiency solar energy conversion. However, the inadequate advanced organic ligands and modification largely hinder their application. In this work, competitive evolution-morphological and structural change from Zn-based crystallites to amorphous particles is achieved. The controllable contribution of organic linkers selectively derived six Zn-CPPs with multivariate characters. Based on the diversity of these substructures, hollow zinc oxide particles were initially formed by self-pyrolysis of CPPs and effectively modified by ultrathin doped-nanosheets. Especially, the obtained double-sided heterojunctions show advantages of fully-covered active sites, bringing together the efficient light-excited charge transfer nanochannels, which exhibit an excellent solar H2 releasing activity (e.g., 4512.5 μmol h-1 g-1 ) and stable cyclability.

White-light Emission and Circularly Polarized Luminescence from a Chiral Copper(I) Coordination Polymer through Symmetry-Breaking Crystallization.

Abstract: Achieving white-light emission, especially white circularly polarized luminescence (CPL) from a single-phase material is challenging. Herein, a pair of chiral Cu(I) coordination polymers ( 1-M and 1-P ) have been prepared by the asymmetrical assembly of achiral ligands and Cu 2 I 2 clusters. The compounds display dual emission bands and can be used as single-phase white-light phosphors, achieving a "warm"-white-light-emitting diode with an ultra-high color rendering index (CRI) of 93.4 and an appropriate correlated color temperature (CCT) of 3632 K. Meanwhile, corresponding CPL signals with maximum dissymmetry factor | g lum | = 8×10 -3 have been observed. Hence, intrinsic white-light emission and CPL have been realized simultaneously in coordination polymers for the first time. This work gains insight into the nature of chiral assembly from achiral units and offers a prospect for the development of single-phase white-CPL materials.

Atomic-Level Modulation-Induced Electron Redistribution in Co Coordination Polymers Elucidates the Oxygen Reduction Mechanism

Abstract: Regulating the atomic arrangement and electron redistribution is beneficial for tuning catalytic oxygen reduction reaction (ORR) performance and deciphering the intrinsic mechanism. Herein, we modulate the charge density around Co centers by designing and synthesizing three Co coordination polymer catalysts, including Co-DABDT (DABDT = 2,5-diaminobenzene-1,4-dithiol, Co–N2S2), Co-BTT (BTT = 1,2,4,5-tetramercaptobenzene, Co–S4), and Co-BTA (BTA = 1,2,4,5-benzenetetramine, Co–N4), to explore the structure–activity relationship between the coordination environment and ORR performance. Because of the high electronegativity of S compared to N atoms, the charge density of Co increases in the order of Co-BTA → Co-DABDT → Co-BTT. Experimentally, Co-DABDT@CNTs with Co–N2S2 delivers a remarkable half-wave potential of 0.85 ± 0.002 V, outperforming Co–N4 and Co–S4 and even Pt/C (0.84 ± 0.003 V). Zinc–air batteries using Co-DABDT@CNTs as the air cathode catalyst also demonstrate excellent power density and stability. The systematic characterization and theoretical simulation reveal that the charge redistribution on Co and S sites of Co–N2S2 would both effectively optimize and stabilize the key intermediate (OOH*) with the assistance of hydrogen bonding interactions between intermediates and active S atoms (*OO–H···S). Interpreting the mechanism of ORR in the coordination sphere provides a feasible way to improve catalytic activity at an atomic level.

Regulating the metal nodes of 1D conjugated coordination polymers for enhancing the performance of sodium-ion batteries

Abstract: 1D conjugated coordination polymers M-DHBQ (M = Mn, Zn, and Ni) were constructed for sodium-ion batteries. Ni-DHBQ delivered the highest performance. These results highlighted the importance of metal ions for high performance batteries.

New photochromic-ligand-based luminescent coordination polymer as MnO4- sensor with extremely high sensitivity and excellent selectivity

Abstract: Photochromic materials have attracted considerable attention because of their promising applications. Herein, the first dihydroanthracene-based photochromic organic ligand 9,10-bis(di(pyridine-4-yl)methylene)-9,10-dihydroanthracene (L) was successfully synthesized. Its photochromic mechanism has been elucidated. The...

Development of magnetocaloric coordination polymers for low temperature cooling.

Abstract: Caloric materials have attracted significant interest as replacements for conventional refrigeration, which is becoming increasingly important in our daily lives, yet poses issues for sustainability due to both energy consumption and loss of refrigerants into the atmosphere. Among caloric materials, which are key to solid state cooling technologies, those exhibiting the magnetocaloric effect (MCE), an entropy-driven phenomenon under cycled applied magnetic fields, are promising candidates for cryogenic cooling. These have potential to replace conventional cryogenics, particularly liquid He - an increasingly scarce and expensive resource. Amongst magnetocalorics, coordination polymers containing polyatomic ligands have been shown to be very promising materials due to their large entropy changes at low temperatures. One of the contributing factors to this peformance is their unique structural flexibility, as they can adopt a wide range of structures usually not accessible for conventional materials, such as close-packed metal oxides. The most researched materials for magnetocaloric applications are those containing Gd as their magnetic centre, as the combination of structure and the weakly interacting 4f orbitals of Gd3+ in these materials enables the fabrication of promising magnetocalorics that contain a high density of cations and thus exhibit a high entropy change as a function of their weight and volume at ultra-low cryogenic temperatures. Alongside this, there is a growing interest in magnetocaloric coordination polymers with their magnetocaloric effect optimised for lower applied fields that can be generated using permanent magnets through incorporating other magnetic cations, including lanthanides with greater magnetic anisotropy. When combined with tailored magnetic interactions this leads to promising entropy changes above 4 K, a typical base temperature for many cryogenic applications. This review discusses the most promising magnetocalorics among coordination polymers and MOFs, highlighting their structural characteristics, and concluding with a brief perspective on the future of this field.

Facile synthesis of a glutathione-depleting Cu(II)-half-salamo-based coordination polymer for enhanced chemodynamic therapy.

Abstract: Chemodynamic therapy (CDT), utilizing Fenton catalysts to convert intracellular H2O2 into toxic hydroxyl radicals (˙OH) to kill cancer cells, has a wide application prospect in tumor treatment because of its high selectivity. Its anticancer effect, however, is unsatisfactory due to the overexpressed glutathione (GSH). Herein, a GSH-depleting Cu(II)-half-salamo-based coordination polymer (CuCP) was prepared and validated by single crystal X-ray crystallography, Hirshfeld surface analyses and DFT calculations. The Cu(II) ions in the coordination polymer are five-coordinated bearing slightly twisted square pyramidal coordination environments and are bridged by phenoxy and alkoxy groups. After internalization by tumor cells, the CuCP could be biodegraded and reduced by GSH to generate a large amount of Cu(I), simultaneously depleting GSH. Subsequently, the Cu(I) ions interact with H2O2 to generate toxic ˙OH through a Fenton-like reaction to enhance their anticancer efficacy. Our study provides useful insights into designing smarter metal-based anticancer agents to improve the CDT efficiency in cancer therapy.

High performance Li-, Na-, and K-ion storage in electrically conducting coordination polymers

Abstract: Coordination polymers (CPs) made of redox-active organic moieties and metal ions emerge as an important class of electroactive materials for battery applications. However, the design and synthesis of high voltage alkali-cation reservoir anionic CPs remains challenging, hindering their practical applications. Herein, we report a family of electrically conducting alkali-cation reservoir CPs with the general formula of A2-TM-PTtSA (wherein A = Li+, Na+, or K+; TM = Fe2+, Co2+, or Mn2+; and PTtSA = benzene-1,2,4,5-tetra-methylsulfonamide). The incorporation of transition metal centers not only enables intrinsic high electrical conductivity, but also shows an impressive redox potential increase of as high as 1 V as compared to A4-PTtSA analogues, resulting in a class of organometallic cathode materials with a high average redox potential of 2.95–3.25 V for Li-, Na- and K-ion batteries. A detailed structure – composition – physicochemical properties – performance correlation study is provided relying on experimental and computational analysis. The best performing candidate shows excellent rate capability (86% of the nominal capacity retained at 10C rate), remarkable cycling stability (96.5% after 1000 cycles), outstanding tolerance to low carbon content (5 wt%), high mass loading (50 mg cm−2), and extreme utilisation conditions of low earth orbit space environment tests. The significance of the disclosed alkali-ion reservoir cathodes is further emphasized by utilizing conventional Li-host graphite anode for full cell assembly, attaining a record voltage of 3 V in an organic cathode Li-ion proof-of-concept cell.

Sustainable Coordination Polymer-Based Catalyst and Its Application in the Nitroaromatic Hydrogenation under Mild Conditions.

Abstract: Nitroarene reduction has played a crucial role in the environment remediation and public health. However, few research studies have been undertaken regarding the use of infinite coordination polymer-based catalysts in this process. Herein, we are looking for a way to catalyze the reduction of nitroarenes using a new and well-designed coordination polymer-based palladium catalyst. The Co-BDC-NH2 coordination polymer was prepared through a co-precipitation reaction between 2-amino-1,4-benzenedicarboxylic acid as a linker and the cobalt cation as a node. Functionalization of the prepared Co-BDC-NH2 with 2-pyridinecarboxaldehyde and subsequent metallation with a Pd cation led to the formation of the final catalyst, i.e., Co-BDC-NH2-py-Pd. It has been specified that palladium species substantially contribute to the reduction of nitroarenes in the presence of hydrazine hydrate (N2H4·H2O). The highest conversion (100%) of nitroarenes to the corresponding amines was achieved under relatively mild conditions. This heterogeneous catalyst was able to catalyze the reduction of nitroarenes to desired products without changing other substituents. The reusability and stability of the catalyst were confirmed through four consecutive reduction tests without a major decrease in catalytic activity.

Tuning chain topologies and magnetic anisotropy in one-dimensional cobalt(II) coordination polymers via distinct dicarboxylates

Abstract: Based on a terpyridine derivative and two different dicarboxylate ligands, two new cobalt(II) coordination polymers, namely [Co(pytpy)(DClbdc)]n (1) and [Co(pytpy)(ndc)]n (2) (pytpy = 4'-(4-Pyridyl)-2,2':6',2''-terpyridine, H2DClbc = 2,5-Dichloroterephthalic acid, and H2ndc...

Evidence for surface effects on the intermolecular interactions in Fe(<scp>ii</scp>) spin crossover coordination polymers

Abstract: From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), it is evident that the spin state transition behavior of Fe(II) spin crossover coordination polymer crystallites at the surface differs from the bulk. A comparison of four different coordination polymers reveals that the observed surface properties may differ from bulk for a variety of reasons. There are Fe(II) spin crossover coordination polymers with either almost complete switching of the spin state at the surface or no switching at all. Oxidation, differences in surface packing, and changes in coordination could all contribute to making the surface very different from the bulk. Some Fe(II) spin crossover coordination polymers may be sufficiently photoactive so that X-ray spectroscopies cannot discern the spin state transition.

Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition

Abstract: Open AccessCCS ChemistryRESEARCH ARTICLE5 Sep 2022Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition Yi-Fei Deng, Yi-Nuo Wang, Xin-Hua Zhao and Yuan-Zhu Zhang Yi-Fei Deng Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055 Google Scholar More articles by this author , Yi-Nuo Wang Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055 Google Scholar More articles by this author , Xin-Hua Zhao Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055 Google Scholar More articles by this author and Yuan-Zhu Zhang *Corresponding author: E-mail Address: [email protected] Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055 Google Scholar More articles by this author https://doi.org/10.31635/ccschem.021.202101407 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The engineering of switchable materials with controllable stimuli-responsive multistability remains challenging in materials science. Herein, we present syntheses and structural and magnetic studies of a one-dimensional cobalt(II) coordination polymer [(enbzp)Co(bpy)](ClO4)2·MeOH·H2O ( 1; enbzp = N,N′-(ethane-1,2-diyl)bis(1-phenyl-1-(pyridin-2-yl)methanimine, bpy = 4,4′-bipyridine) and its desolvated analogue [(enbzp)Co(bpy)](ClO4)2 ( 2), obtained by reversible single-crystal-to-single-crystal (SCSC) transformation. Both complexes feature a rigid cationic chain with alternate enbzp-chelated Co(II) units and bpy linkers and exhibit incomplete and gradual spin crossover (SCO) behavior while, interestingly, additional thermally induced nonspin bistability was only observed in 2. Remarkably, the nonspin bistability shows an unprecedented scan-rate selectivity with a 75 K shift of center temperatures. At a rate above 5 K/min (fast-cooling), the transition takes place solely in the temperature range of 225–240 K centered at about 230 K with a hysteresis loop of 14 K, while at rates below 0.5 K/min (slow-cooling), the dynamic bistability moves to the room-temperature region (∼305 K) with wider hysteresis loops (∼26 K). Further studies revealed that the “slow-cooling” coupled transition occurs synchronously with the conformational swing of the cationic [(enbzp)Co(bpy)]2+ units and displacement of the [ClO4]− anions. The “fast-cooling” situation, however, could not be followed due to the rapid and irreversible structural rearrangement toward the more thermodynamically stable phase, as confirmed by time-dependent structural characterization and magnetic relaxation studies. These physical properties strongly corroborate that the two separated thermal bistability states as well as the multimagnetic states can be selected at will, based on the kinetics of subtle structural changes or rearrangements with different temperature-scan rates, which may be promoted to the memory devices armed with multichannels and functionalized in a desired manner. Download figure Download PowerPoint Introduction The engineering of switchable molecules with dramatic magnetic changes has been one of the most active areas of research worldwide , due to their potential applications for the next generation of switching, sensor, and memory devices.1–3 Among the most studied systems are spin crossover (SCO) compounds,4–6 in which the dramatic magnetic changes originate from spin transition between high-spin (HS) and low-spin (LS) states, which may be triggered by external stimuli such as temperature,7,8 light,9,10 and pressure.11,12 In addition to significant changes in magnetism, modulation of spin states may also synergize with other functionalities, such as electrical conductivity,13,14 ferroelectric property,15,16 negative thermal expansion,17,18 and luminescence,19,20 indicating the suitability of these molecules for multifunctional materials. Moreover, magnetic changes may be also achieved in a nonspin switching manner, induced by the so-called structural phase transition (SPT), such as order/disorder rearrangement,21,22 dynamic coordination bond breakage/formation,23 ligand rotation,24 and cis–trans isomerism.25 Consequently, the incorporation of both spin and nonspin transitions (SCO + SPT) in one molecule has provided a new promising strategy for the construction of multifunctional systems, which are useful for multiswitching and ternary memory devices.26,27 Representative examples can be found in a series of mononuclear SCO complexes equipped with long alkyl chains, known as soft SCO compounds,28,29 in which the SCO event is associated with the molecular-level motions of the flexible alkyl chains in either a nonsynchronous way at different temperature regimes or by being strongly synergized at the same temperature region, leading to unexpected physical properties. For example, Hayami et al.30,31 presented the unique SCO behavior of “reverse spin transition” or “re-entrant SCO,” triggered by the thermal motion of the long alkyl chains that are attached to the terpyridine-like ligands of the cationic cobalt(II) complexes. Real and co-workers32 demonstrated the sweeping-dependent SCO processes caused by the isostructural phase transition in an alkyl-tailed mononuclear iron(II) complex. Recently, Clérac and co-workers33 observed the tristability in an iron(II) SCO compound, in which the non-SCO bistability was caused by the anti/gauche change of the decorated alkyl chains. Progress notwithstanding, systems featuring such synergy are extremely limited. With our long-standing interest in magnetically switchable materials,34,35 we recently prepared a few [FeIII2FeII] SCO complexes based on a series of tetradentate ligands armed with different aromatic rings, interestingly, those of the right size may rotate and thus induce an order/disorder rearrangement.36,37 We proposed extending this strategy into a rigid polymeric crystal lattice in which the effect of such atomic-level structural changes on the magnetic behavior may be significantly amplified due to the enhanced cooperativity38,39 between the SCO centers. Herein, we report the syntheses and structural and magnetic studies of a one-dimensional (1D) cobalt(II) coordination polymer, [(enbzp)Co(bpy)](ClO4)2·MeOH·H2O ( 1; enbzp = N,N′-(ethane-1,2-diyl)bis(1-phenyl-1-(pyridin-2-yl)methanimine, bpy = 4,4′-bipyridine) and its desolvated phase [(enbzp)Co(bpy)](ClO4)2 ( 2), obtained through reversible single-crystal-to-single-crystal (SCSC) transformation. Both 1 and 2 showed gradual SCO behavior, while additional nonspin bistability with bulk hysteretic behavior during the SCO event was clearly observed in 2, which exhibited unique selectivity with the temperature scan rates. Playing with the slow kinetics of related structural changes, four distinguishable magnetic states including the high-temperature (HT) state (S1), the intermediate state (S2), the dynamically metastable low-temperature (LT) state (S3), and the thermodynamically stable LT state (S4) are discussed. A slow (<0.5 K/min) or fast scan rate (> 5 K/min) would initialize the S1→S4 or S2→S3 magnetic transition, thus leading to the two distinct thermal bistabilities centered at about 305 and 230 K, respectively. Moreover, both the intermediate and dynamically metastable phases would convert to the thermodynamically stable phase via a structural rearrangement-induced relaxation process, as corroborated by the time-dependent structural characterization and magnetic relaxation studies. Experimental Methods Materials and syntheses Enbzp was prepared according to the literature.40 All other chemicals and reagents were commercially available and used without further purification. Caution: Although no such issues were observed during the present work, perchlorate salts are potentially explosive and should be handled in small quantities and with great care. Synthesis of [(enbzp)Co(bpy)](ClO4)2·MeOH·H2O (1) A methanolic solution (5 mL) containing Co(ClO4)2·6H2O (36.5 mg, 0.10 mmol) and enbzp (39.1 mg, 0.10 mmol) was allowed to stir for 30 min at 45 °C in an ambient atmosphere. After cooling to room temperature, the mixture was filtered; 4,4′-bipyridine (15.6 mg, 0.10 mmol) in 4 mL MeOH was subsequently added into the purple filtrate, and the resulting solution was left to evaporate slowly to yield the red crystals of 1. The product was collected by filtration and washed with methanol. Yield 66.7 mg (78%). Anal. Calcd for C37H36Cl2CoN6O10: C, 52.00; H, 4.25; N, 9.83. Found: C, 51.84; H, 4.46; N, 9.77. Fourier transform infrared (FT-IR) data (cm−1): 3751 (w), 3649 (w), 3076 (w), 2945 (w), 2825 (w), 2021 (w), 1599 (s), 1541 (m), 1444 (m), 1408 (s), 1359 (m), 1336 (m), 1267 (m), 1220 (m), 1164 (m), 1076 (vs), 817 (s), 794 (s), 742 (s), 700 (s), 621 (vs). It should be mentioned that complex 1 was also obtained by inserting an open vial with the crystalline sample of 2 in a closed cell with the humid methanol vapor atmosphere overnight. The resulting crystals [email protected] were found to be the same as 1, confirmed by both the single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD). Anal. Calcd for C37H36Cl2CoN6O10: C, 52.00; H, 4.25; N, 9.83. Found: C, 51.76; H, 4.34; N, 9.68. FT-IR data (cm−1): 3750 (w), 3649 (w), 3078 (w), 2945 (w), 2827 (w), 2019 (w), 1596 (s), 1539 (m), 1442 (m), 1410 (s), 1361 (m), 1337 (m), 1267 (m), 1218 (m), 1164 (m), 1076 (vs), 815 (s), 792 (s), 742 (s), 700 (s), 621 (vs). Synthesis of [(enbzp)Co(bpy)](ClO4)2 (2) Single crystals of 2 were quantitatively prepared by thermal desolvation of the crystalline sample of 1 at 350 K and under continuous nitrogen flow for 1 h. Anal. Calcd for C36H30Cl2CoN6O8: C, 53.75; H, 3.76; N, 10.45. Found: C, 53.69; H, 3.81; N, 10.35. FT-IR data (cm−1): 3750 (w), 3649 (w), 3075 (w), 2945 (w), 2827 (w), 2156 (m), 2005 (w), 1596 (s), 1541 (m), 1444 (m), 1408 (s), 1360 (m), 1335 (m), 1261 (m), 1220 (m), 1163 (m), 1074 (vs), 817 (s), 792 (s), 742 (s), 700 (s), 621 (vs). Physical measurements X-ray crystallographic data SCXRD measurements for 1 at 110–300 K ( Supporting Information Table S1) and 2 at 400–200 K ( Supporting Information Tables S2–S4) were performed using a Bruker D8 VENTURE diffractometer (Germany) with graphite monochromated Mo Kα radiation (λ = 0.71073 Å). Select bond distances and angles are listed in Supporting Information Tables S5–S8. The fully desolvated crystal of 2 was obtained via in situ thermal desolvation of 1 at 350 K on the diffractometer for 30 min, and it was then measured successively at 360, 370, 400, 360, 350, 330, 300, 290, 280, 270, 230, and 200 K, respectively, using a sweeping rate of 0.5 K/min between the measurements. Furthermore, to probe the relaxation-coupled structural rearrangement, the crystal of 2 was cooled from 350 to 270 K at 6 K/min, and then one dataset ( 2270-1) was quickly collected. After standing for an additional 5 h at 270 K, another dataset ( 2270-2) was then collected. A similar procedure at 200 K was applied for 2200-1 and 2200-2. All the structures were solved by the direct method of SHELXT41,42 and refined by full-matrix least squares (SHELXL) on F2, and empirical absorption corrections (SADABS)43 were applied. Anisotropic thermal parameters were used for the nonhydrogen atoms. Hydrogen atoms were added geometrically and refined using a riding model. CCDC 2070353 ( 1300), 2070354 ( 1110), 2070355 ( [email protected]300), 2070356 ( 2360h), 2070357 ( 2370), 2070358 ( 2400), 2070359 ( 2360c), 2070360 ( 2350), 2070361 ( 2330), 2070362 ( 2300), 2070363 ( 2290), 2070364 ( 2280), 2070365 ( 2270), 2070366 ( 2230), 2070367 ( 2200), 2070368 ( 2270-1), 2070369 ( 2270-2), 2070370 ( 2200-1), and 2070371 ( 2200-2) contain the crystallographic data that can be obtained via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ, UK; fax: (+44) 1223-336-033; or [email protected]). Elemental analysis Elemental analyses (EA) (C, H, N, and S) were measured by a vario electroluminescence (EL) cube CHNOS Elemental Analyzer (Elementar Analysensysteme GmbH, Germany). FT-IR spectroscopy FT-IR spectra were recorded in the range 600–4000 cm−1 using a Bruker TENSOR II spectrophotometer (Germany). PXRD Variable-temperature PXRD measurements were performed at 300–400 K (heating) and 400–150 K (cooling) using a Rigaku SmartLab X-ray diffractometer (Japan) with Cu Kα radiation (45 kV, 200 mA) between 5° and 50° (2θ). Thermogravimetric analysis Thermogravimetric analysis (TGA) experiments were performed with fresh samples using a METTLER TOLEDO TGA2 instrument (Switzerland). The TGA curves were measured under an argon atmosphere from 300 to 800 K with a heating rate of 5 K/min. Differential scanning calorimeter experiment Differential scanning calorimeter (DSC) measurements were recorded at 150–380 K and 260–330 K with a temperature scan rate of 5 and 0.5 K/min, respectively, using a TA Instruments Discovery DSC2500 (USA). Specific heat experiment Specific heat measurements were performed with the desolvated sample using the N-grease as the heat conductor, recorded with a PPMS DynaCool-9T system. The average sweeping rate was estimated as 0.1 K/min based on the log data file. To eliminate the perturbation from the N-grease, the heat capacity of different sets of samples as well as the related backgrounds have been carefully measured for several times, and the overall specific heat data for the sample was well reproduced after subtracting the contributions of the background. Magnetic measurements Magnetic measurements were performed using a superconducting quantum interference device (SQUID) MPMS3 magnetometer (USA). Specifically, the freshly prepared crystals were slightly ground and then placed into a capsule for SQUID brass, and the measured magnetic properties were consistently found in different batches of crystal samples. In the sweeping mode the magnetic data were recorded in the temperature range 350–150 K at rates 10, 5, 2, 0.5, and 0.25 K/min, respectively; while in the settle mode the magnetic data were further recorded in the temperature range 350–200 K with an average scan rate of 0.51 K/min. For the additional scan-rate-dependent magnetic measurements in two different procedures: (1) the sample was always cooled from 350 to 150 K at 10 K/min, while heated back to 350 K at 5, 1, 0.25, and 0.1 K/min, respectively; (2) the sample was always cooled from 350 to 150 K at 0.25 K/min, while heated back to 350 K at 10 and 1 K/min, respectively. For the relaxation experiments, the sample was initially cooled at 10 K/min from 350 K to the desired temperature, and then the susceptibility was monitored over time at the desired temperature. Magnetic data were corrected for the diamagnetism of the sample holder and for the diamagnetism of the sample using Pascal’s constants.44 Results and Discussion Syntheses and crystallographic studies Treatment of Co(ClO4)2·6H2O and enbzp in a 1∶1 ratio in methanol followed by addition of equivalent 4,4′-bipyridine in an ambient atmosphere gave the dark red crystals of 1 in quantitative yield in a few days. TGA analysis ( Supporting Information Figure S1) revealed a fast weight loss of 5.9% from 300 to 350 K, corresponding to the removal of one MeOH and one H2O molecule per formula unit (calculated 5.9%); the following broad platform up to 500 K before the complete decomposition at 550 K well indicated the robust thermal-stability of the desolvated phase, which was found to be a new crystalline state ( 2), confirmed by the in situ desolvation of 1 on the X-ray diffractometer as well as the powder XRD analysis (vide infra). Accordingly, the bulk sample of 2 was prepared by heating the crystalline sample of 1 at 350 K for 1 h under a nitrogen atmosphere. Moreover, the single crystals of 2 may be resolvated and turn back to 1 when they are maintained overnight within the humid MeOH vapor atmosphere, suggesting a reversible SCSC transformation between 1 and 2. The SCXRD study revealed that complex 1 crystallized in the orthorhombic space group Pbca; and the asymmetric unit contained a cationic [(enbzp)Co(bpy)]2+ fragment, two [ClO4]−, one MeOH and one water molecule (Figure 1). The Co(II) ion adopts a distorted octahedral [CoN6] environment, with four equatorial N atoms of enbzp, and two axial N atoms of bpy ligands that linked the adjacent metal centers into a 1D coordination chain along the c-axis. Owing to the rigidity of the chelating enbzp ligand, the equatorial Co–N bond length (1.891(3)–2.020(3) Å) at 300 K were significantly shorter than the Co–N axial bonds (2.347(3) and 2.240(3) Å), leading to a pronounced elongation along the axial sites. These bond distances with the average value of 2.068 Å were considerably shorter than those of pure HS Co(II) compounds but in good agreement with a mixture of both HS and LS Co(II) species (vide infra). Upon cooling to 110 K, the Co–N bond lengths shrank slightly to 1.872–2.315 Å with an average value of 2.047 Å, suggesting the possible presence of the SCO process. In the crystal packing, the adjacent chains were coupled by significant π···π interaction (3.656–4.073 Å) between the aromatic rings in enbzp–enbzp or enbzp–bpy ligands to form a quasilayer structure ( Supporting Information Figure S2); the layers were further weakly bridged by extensive anion···π coupling (3.100–3.758 Å) dictated by the [ClO4]− anions and bpy rings, and edge-to-egde π···π interactions (3.768 Å) between enbzp ligands to generate a 3D network ( Supporting Information Figure S3). The remaining crystal volume was occupied by the interstitial solvent molecules of MeOH and H2O. Figure 1 | Crystal structures of 1 (top) and 2 (bottom, with disorders in the aromatic rings of enbzp) along c-axis showing the reversible SCSC transformation and conformational changes in bpy ligands. Color codes: Co, purple; C, grey; N, blue; O, red. Hydrogen atoms and counterions are omitted for clarity. Download figure Download PowerPoint Complex 2 crystallized in the same orthorhombic space group Pbca, which however underwent the change to Cmcm at above 370 K, and recovered when cooled back in situ to 350 K and underwent no further change upon further cooling to 200 K. Enclosed within the chain, the coordination environment including the axially elongated geometry and Co–N bond lengths in 2 are similar to those in 1 while the bpy-bridged skeletons were different (Figure 1). Specifically, a significant twist of bpy bridges led to a “zig-zag” chain structure in 1, which however becomes almost straight and planar in 2, as indicated by the change of intra Co–Co–Co angles ( 1, 175.15°; 2, 179.91°) and the dihedral angles (θ) for bpy ligands ( 1, 12.34°; 2, 1.68°). Extensive short contacts were also found for 2 throughout the 3D packing arrangement involving the weak anion···π couplings (3.147–3.883 Å), face-to-face (3.712 Å), and edge-to-edge (4.143 Å) π···π interactions ( Supporting Information Figures S4 and S5). Magnetic studies Variable-temperature magnetic susceptibility for 1 and 2 was collected in the 2–400 K temperature range with an applied direct current (dc) field of 1 kOe (Figure 2). For 1, the χT product of 0.76 cm3 K mol−1 at 300 K suggested a mixture of HS and LS Co(II) species. Upon cooling, the χT product decreased continuously to 0.37 cm3 K mol−1 at 12 K, in agreement with the pure LS phase. When the temperature increased, the χT product followed the same variation as observed in the cooling mode before a jump between 312 K (0.85 cm3 K mol−1) and 320 K (0.83 cm3 K mol−1), and then increased steadily to 1.26 cm3 K mol−1 at 400 K, suggesting the gradual and incomplete SCO transition over the entire temperature range (Figure 2a). In terms of the TGA study, the jump can be attributed to the loss of the interstitial solvent molecules. The HT nonsaturation was likely caused by the rigidity of the chelating enbzp ligand around the Co(II) centers. No abnormality in the evolution of the χT product was observed at around 360 K where the Pbca↔Cmcm transition proceeded, possibly due to the negligible structural and thermal changes, as indicated by the SCXRD and DSC studies (vide infra). Figure 2 | Variable-temperature χT plots for 1 (a) recorded on cooling→heating with a scan rate of 5 K/min, and for 2 (b) at 350–150 K with different scan rates. S1–S4 states are described in the text. Solid lines are guides for the eye. Download figure Download PowerPoint Nevertheless, the sample of 1 was continuously maintained at 400 K for 20 min in the magnetometer to ensure the complete desolvation to 2. Upon lowering the temperature with the scan rate of 5 K/min, the χT product gradually decreased from 1.26 cm3 K mol−1 at 400 K to 0.31 cm3 K mol−1 at 2 K, indicating the overall gradual SCO process. Surprisingly, an abrupt increase from 0.58 cm3 K mol−1 at 226 K to 0.62 cm3 K mol−1 at 220 K was observed ( Supporting Information Figure S6), which moved toward the higher temperature range at between 234 (0.68 cm3 K mol−1) and 246 K (0.63 cm3 K mol−1) on heating back at the same scan rate, resulting in a thermal bistability (T1/2↓ = 223 K, T1/2↑ = 237 K) with a hysteresis loop of about 14 K (Table 1). This abrupt increase was most likely caused by the SPT-induced changes in the orbital angular momentum or magnetic interaction, rather than to a reverse spin transition (vide infra). Remarkably, this thermal bistability showed an unprecedented dependence on the temperature scan rates (Figure 2b). Specifically, at a faster scan rate (10 K/min), the χT – T plot showed a similar thermal hysteretic behavior with larger change in magnetization at between T1/2↓ = 222 K and T1/2↑ = 238 K. However, after applying a slower scan rate of 2 K/min, the transition centered at about 228 K (T1/2↓ = 222 K, T1/2↑ = 234 K) got less significant with another coalesced hysteresis loop appearing at HT range (T1/2↓ = 280 K, T1/2↑ = 320 K). With more slower scan rates (0.5 or 0.25 K/min), the thermal bistability only appeared at the HT range (0.5 K/min, T1/2↓ = 292 K, T1/2↑ = 318 K; 0.25 K/min, T1/2↓ = 294 K, T1/2↑ = 316 K) with the loops of 26 and 22 K, respectively. It should be noted that the hysteretic profiles of 2 at a given scan rate (5 and 0.5 K/min) were reproducible over two cycles of measurements ( Supporting Information Figure S7). Table 1 | The Transition Temperatures for the Thermal Hysteresis of 2 at Different Scan Rates Scan Rate (K/min) T1/2↓ (K) T1/2↑ (K) ΔT (K) Tcenter (K) 10 222 238 16 230 5 223 237 14 230 2 222 234 12 228 280 320 40 300 0.5 292 318 26 305 0.25 294 316 22 305 For most of the hysteretic SCO systems, the lower transition temperatures observed in the “fast-cooling” process are usually caused by a temperature lag associated with the quench effect of HS state during the HS→LS conversion, which would correspondingly elevate the transition temperatures upon heating and thus expand the thermal hysteresis. However, a few SCO complexes were recently reported to show “abnormal” hysteretic properties beyond this rule,45–47 in which additional SPTs were often found. For example, a few reports described a reverse trend where the slower scan rates led to the higher transition temperature and wider hysteresis, and revealed the coexistence of two LS states, which may be switched through a SPT.32,45–47 We presumed that the present system has four possible thermal states (S1–S4, Figure 2b), where S1 represents the HT state; S2 for the intermediate state; S3 for the dynamically metastable LT state; and S4 for the thermodynamically stable LT state. The transitions between these four states might account for the intriguing magnetic properties. For the cooling process, with slow temperature-scan rates (<0.5 K/min), the S1→S4 magnetic transition is operative due to the sufficient time delay during the measurements, leading to the HT transition. Fast scan rates (>5 K/min) would quench this transition leading to the LT transition S2→S3 (intermediate state to dynamically metastable state). With a moderate temperature-scan rate (2 K/min), the two thermal bistabilities can overlap in a large temperature range where both the transitions occurred. Assuming that the entire gradual SCO process is synchronized with another nonspin magnetic transition caused by the subtle structural changes featuring very slow kinetics, two well-separated thermal bistability domains are realized. Accordingly, the hypothesis is probed by the cycles of successive χT measurements using different scan rates for the cooling and heating branches. In the first case, the sample was always cooled from 350 to 150 K at 10 K/min to reach the S3 phase, and then the magnetic susceptibility data were recorded on warming back with different scan rates (Figure 3a). A heating starting in the S3 phase at 5 K/min shows a jump at about 236 K that corresponds to the reversible S3→S2 transition. With decreasing the scan rates, this marked jump in χT products decreases continuously to vanish at a scan rate of 0.1 K/min, which is indicative of the S3→S4 relaxation. On the other hand, the cooling process was always conducted at 0.25 K/min to guarantee the S4 state, and then the sample was heated at different scan rates (Figure 3b). As expected, once the thermodynamically stable S4 phase was achieved, it would not convert to any other states except for the reversible S4→S1 transition at HTs. Moreover, the relaxation kinetics were further investigated by following the time evolution of the intermediate states (Figure 3c and Supporting Information Figure S8). As a result, the χT vs time plots underwent significant increase in the magnetization for the temperatures at 200–290 K. These results clearly reveal the S2→S4 and S3→S4 relaxation, which may be caused by the structural rearrangements toward the more favorable thermodynamically stable phase (vide infra). These results demonstrate that both the “fast-cooling” dynamic metastable state and the intermediate state relaxes to the more stable “slow-cooling” phase, supporting the finding that the double transitions are coupled with dynamic and thermodynamic states that are associated with the fast and slow scan rates, respectively (Figure 3d). Figure 3 | (a) Variable-temperature χT vs T plots for 2 upon cooling at fixed 10 K/min and heating at 5, 1, 0.25, and 0.1 K/min, respectively. (b) Variable-temperature χT vs T plots for 2 upon cooling at fixed 0.25 K/min and heating at 10 and 1 K/min, respectively. (c) Time evolution of the magnetic susceptibility for 2 at the selected temperatures. (d) Schematic view of the magnetic transitions between the S1–S4 states. Solid lines are guides for the eye. Download figure Download PowerPoint PXRD studies The reversible SCSC transformation for bulk crystalline samples between 1 and 2 was investigated by a PXRD method. At room temperature, the PXRD patterns for 1 and 2 matched well with their SCXRD simulations, indicating the successful desolvation process for 1 and the good purity of both samples. After exposing the crystalline sample of 2 to the humid methanol vapor atmosphere overnight, the experimental PXRD pattern matches well with that found for 1, demonstrating the reversibility of the desolvation and solvation processes ( Supporting Information Figure S9). Moreover, the desolvation driven structural transformation and the validity of structural models for the bulk samples was well tracked by means of in situ variable-temperature PXRD experiments (Figure 4 and Supporting Information Figure S10). Upon heating from 300 to 350 K, the peak at 20.69° ({420} facets) underwent a continuous shift to 20.88°, likely due to the loss of interstitial solvent molecules located at these interfaces ({420} facets). At above 360 K, the peaks at ca. 12.76° and 13.52° disappeared, likely due to the Pbca→Cmcm transition. On the subsequent cooling process, the reversible Cmcm→Pbca transition was detected at 350 K as indicated by the recovery of the peaks at 12.79° and 13.54°; moreover, the continuous shift of the peak at 20.78° (350 K) to 21.28° (150 K) can possibly be ascribed to the gradual SCO-related structur

Syntheses, structures, and luminescent properties of five new coordination polymers based on 3-carboxy-1-(3’-carboxy-benzyl)-2-oxidopyridinium and neutral ligand

Abstract: A series of coordination polymers, namely, [Zn(μ3-L)(H2O)2] (1), [Zn(μ2-L)(2,2’-bpy)(H2O)] (2), [Zn(μ3-L)(μ2-4,4’-bpy)0.5] (3), [Cd(μ3-L)(2,2’-bpy)] (4), and [Cd(μ2-L)(phen)(H2O)] (5) (H2L = 3-carboxy-1-(3’-carboxy-benzyl)-2-oxidopyridinium, 2,2’-bpy = 2,2’-bipyridine, 4,4’-bpy = 4,4’-bipyridine, phen = 1,10-phenanthroline), have...

Circularly polarised luminescence in an RNA-based homochiral, self-repairing, coordination polymer hydrogel

Abstract: The aqueous equimolar reaction of Ag(i) ions with the thionucleoside enantiomer (−)6-thioguanosine, ((−)6tGH), yields a one-dimensional coordination polymer {Ag(−)tG}n, the self-assembly of which generates left-handed helical chains. The resulting helicity induces an enhanced chiro-optical response compared to the parent ligand. DFT calculations indicate that this enhancement is due to delocalisation of the excited state along the helical chains, with 7 units being required to converge the calculated CD spectra. At concentrations ≥15 mmol l−1 reactions form a sample-spanning hydrogel which shows self-repair capabilities with instantaneous recovery in which the dynamic reversibility of the coordination chains appears to play a role. The resulting gel exhibits circularly polarised luminescence (CPL) with a large dissymmetry factor of −0.07 ± 0.01 at 735 nm, a phenomenon not previously observed for this class of coordination polymer.

Four-in-One Multifunctional Air Filter using Copper Coordination Polymer Particle Decorated Fiber for Efficient Pathogen Removal and Indoor Air Treatment

Abstract: This paper introduces a multifunctional air filter with a strong ability to trap and disinfect pathogens and absorb particulate matter (PM), the volatile organic compound (VOC), and CO 2 . This study demonstrates a facile and eco-friendly synthesis of copper coordination polymer particle (Cu-CPP)-decorated non-woven fibre filters (Cu-CPP/NWF) via an in situ growth dip-coating method. Their multifunction potentials in air pollution treatment are also assessed. The Cu-CPP/NWF filter media showed a remarkable performance for air treatment, with 100% disinfection efficiency against airborne E. coli bacteria (2 × 10 6 CFU mL −1 ) in 45 min, superior PM removal efficiency (quality factor 0.299 Pa −1 ), excellent p-xylene adsorption capacities (1.19 mmol/g) and high potential CO 2 uptake capacities (19.81 cm 3 /g). A Cu-CPP can work as an antibacterial agent and an adsorbent component, thus offering many applications. The rational integration of Cu-CPP can substantially enhance the filtration efficiency via electrostatic interaction, while most commercial air purifiers rely on dense fibrous filters. This study provides valuable insight into developing a multifunctional and reusable air filter proven to be a life-saving product for public health protection.

Multicolor-tunable room-temperature afterglow and circularly polarized luminescence in chirality-induced coordination assemblies

Abstract: Dynamic long-lived multicolor room temperature afterglow and circularly polarized luminescence (CPL) are promising for optoelectronic applications, but integration of these functions into a single-phase chiroptical material is still a difficult and meaningful challenge. Here, a nitrogen-doped benzimidazole molecule 1H-1,2,3-triazolopyridine (Trzpy) showing pure organic room-temperature phosphorescence (RTP) acted as a linker, and then, we propose a chirality-induced coordination assembly strategy to prepare homochiral crystal materials. Two homochiral coordination polymers DCF-10 and LCF-10 not only exhibit multicolor-tunable RTP, the color changed from green to orange under various excitation wavelengths, but also show remarkable excitation-dependent circularly polarized luminescence (CPL), and the dissymmetry factors of CPL in DCF-10 and LCF-10 are 1.8 × 10−3 and 2.4 × 10−3, respectively. Experimental and theoretical studies demonstrated that molecular atmospheres with different aggregation degrees give rise to multiple emission centers for the generation of multicolor-tunable emission. The multicolor-tunable photophysical properties endowed LCF-10 with a huge advantage for multi-level anti-counterfeiting. This work opens up new perspectives for the development and application of color-tunable RTP and CPL.